The device used in this work is a high-Q LN coupled double-ring resonators (inset I of Fig. REF ) fabricated from a 600 x-cut thin film LNOI wafer (from NANOLN), originally designed for microwave-to-optics conversion [1]}, [2]}, [3]}. The coupled optical ring resonators have a width of 1.6, with radius 80 and 90 respectively, and a coupling gap of 0.7. The device is patterned by electron beam lithography, with 350-thick LN etched through \(\mathrm {Ar^+}\) -based reactive ion etching. Detailed fabrication process can be found in our previous work [4]}. In the final step, the device is coated with 1.5 silicon dioxide using plasma enhanced chemical vapor deposition.
